This invention relates to annular bore seals for piping devices, and more particularly to such seals constructed of plastic or other non-metallic compositions that are resistant to elevated temperatures and high pressures.
As indicated by the abundant prior art, annular seals of many designs and compositions have been proposed for use in sealing the bores of various piping devices such as pipe connectors, pipe swivel joints, valves and other oil well drilling and completion equipment, and the results achieved therewith likewise have been varied. Many seals currently used in such devices are made from elastomers which have inherent limitations with respect to extrusion, fluid incompatibility, temperature range, creep, and explosive decompression, i.e. seal rupture resulting from the escape of gas that has permeated the elastomer at high pressure and temperature, when the pressure on the seal is quickly released. A metal seal is used when dealing with broad temperature ranges, extreme pressures and highly adverse fluid environments, but such seals are limited to static or substantially static applications. Furthermore, metal seals will function satisfactorily only with very smooth seal bore surfaces and will leak if the surface is even lightly scratched. Yet another disadvantage with metal bore seals is that the drag between the seal and the bore surface is much higher than that of elastomeric or plastic bore seals, sometimes requiring a seal puller to remove the metal seal from its chamber or pocket. Very careful handling of metal seals is required, such as during packaging and installation, thereby further increasing the difficulty and cost in providing a satisfactory product of this type.
Accordingly, one object of the present invention is to provide a plastic bore seal that will function satisfactorily at high pressures and temperatures in either a static or dynamic mode in a wide variety of piping devices including, for example, conventional pipe connectors and swivel joints. Another object of the present invention is to provide a plastic bore seal that can be used as an alternative to a metal seal counterpart without having to redesign the piping device pocket or chamber in which the seal resides.